Acid and enzyme hydrolysis to convert pretreated lignocellulosic materials into glucose for ethanol production

Improved Sugar Recovery of Alkaline Pre-Treated Pineapple Leaf Fibres via Enzymatic Hydrolysis and Its Enzymatic Kinetics

The biofibre complex structure in pineapple leaf fibres (PALFs) can be disrupted using the alkaline pre-treatment method with sodium hydroxide (NaOH). Nonetheless, the pre-treated structures have an impact on the bioconversion of PALFs into sugar. Thus, the impact necessitates precise reaction conditions, which are required for the enzymatic hydrolysis of PALFs. In this study, the Box–Behnken design (BBD) was utilised to achieve maximum sugar yield from PALFs. The optimised enzymatic hydrolysis conditions were 229 µg/mL of cellulase, a reaction temperature of 45 °C, and a hydrolysis time of 69 h. Resultantly, an 84% increase in sugar yield was observed, from 17.26 mg/mL to 108.74 mg/mL after the optimisation process. Moreover, a significant influence (p = 0.0009) of the enzymatic hydrolysis on hydrolysis time and temperature was observed. Additionally, the kinetic study analysis of NaOH pre-treatment and the enzymatic hydrolysis process were investigated. The kinetics of enzyme concentrations on total reducing sugar (TRS) production using an insoluble substrate were investigated based on modified Michaelis–Menten and Chrastil models. The result of the models is in good agreement with the experimental data, as the PALF hydrolysis process was reasonably well predicted. This study provides valuable information for predicting the sugar yield of the PALF bioconversion.

Effects of taxifolin from enzymatic hydrolysis of Rhododendron mucrotulatum on hair growth promotion

Flavonoid aglycones possess biological activities, such as antioxidant and antidiabetic activities compared to glycosides. Taxifolin, a flavonoid aglycones, is detected only in trace amounts in nature and is not easily observed. Therefore, in this study, to investigate the hair tonic and hair loss inhibitors effect of taxifolin, high content of taxifolin aglycone extract was prepared by enzymatic hydrolysis. Taxifolin effectively regulates the apoptosis of dermal papilla cells, which is associated with hair loss, based on its strong antioxidant activities. However, inhibition of dihydrotestosterone (DHT), which is a major cause of male pattern hair loss, was significantly reduced with taxifolin treatment compared with minoxidil, as a positive control. It was also confirmed that a representative factor for promoting hair growth, IGF-1, was significantly increased, and that TGF-β1, a representative biomarker for hair loss, was significantly reduced with taxifolin treatment. These results suggest that taxifolin from enzymatic hydrolysis of RM is a potential treatment for hair loss and a hair growth enhancer.

Bio-Conversion of Waste Paper Into Fermentable Sugars—A Review

Pollution generated by solid waste has become a massive source of concern worldwide as the amount of waste being generated has become overwhelming. Waste paper contributes significantly to the overall solid municipal waste being generated daily and with control methods that are equally bad for the environment or just plain ineffective; better, effective, and environmentally friendly control solutions are required. This study reviews the use of various microorganisms as they aid in the control of waste papers in an environmentally conscious way. In addition to being an environmentally friendly solution to the issue of solid waste paper pollution, it is also a prominent source of renewable energy in the conversion of paper into fermentable sugars for the production of bio-ethanol. This review examines the vital revolution in the enzymatic hydrolysis of paper to sugar. Salient challenges that involve bioconversion were highlighted and a few solutions were suggested.

Techno-Economic Analysis on an Industrial-Scale Production System of Polyhydroxyalkanoates (PHA) from Cheese By-Products by Halophiles

Polyhydroxyalkanoates (PHA) are a family of biodegradable plastics used as an ecofriendly alternative for conventional plastics in various applications. In this study, an industrial-scale PHA production system was designed and analyzed for the material flows and economics with the use of SuperPro Designer. Haloferax mediterranei was utilized to produce poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV). Byproduct streams from a local cheese plant, with an input of 168.7 metric ton/day (MT/day) lactose, were used as the feedstock. Three scenarios with different processes for the treatments of used enzyme and spent medium were investigated and the major factors that influence the overall economics were identified. The simulated system produces 9700 MT/year PHBV with a yield of 0.2 g PHBV/g lactose and an overall process efficiency of 87%. The breakeven price was found to be more sensitive to the lactose price than enzyme price. The scenario with enzyme reuse and spent medium recycling achieved the lowest breakeven price among others, which can be less than 4 $/kg PHA based on the delactosed permeate (DLP) unit price. The study suggests utilizing dairy derived feedstocks has the potential to make PHA competitive in the bioplastic market, which could be beneficial to both dairy and bioplastic industries.

The Role of Bioactive Peptides in Diabetes and Obesity

Bioactive peptides are present in most soy products and eggs and have essential protective functions. Infection is a core feature of innate immunity that affects blood pressure and the glucose level, and ageing can be delayed by killing senescent cells. Food also encrypts bioactive peptides and protein sequences produced through proteolysis or food processing. Unique food protein fragments can improve human health and avoid metabolic diseases, inflammation, hypertension, obesity, and diabetes mellitus. This review focuses on drug targets and fundamental mechanisms of bioactive peptides on metabolic syndromes, namely obesity and type 2 diabetes, to provide new ideas and knowledge on the ability of bioactive peptide to control metabolic syndromes.

Enzymatic Hydrolysis and Fermentation of Banana Pseudostem Hydrolysate to Produce Bioethanol

Banana pseudostem (BPS) is an agricultural waste with a high holocellulose content, which, upon hydrolysis, releases fermentable sugars that can be used for bioethanol production. Different pretreatment methods, namely, 3% (w/v) NaOH, 5% (v/v) H₂SO₄, and liquid hot water, applied on the BPS resulted in the availability of 52%, 48%, and 25% cellulose after treatment, respectively. Saccharification of the pretreated BPS with 10 FPU/g dry solids (29.3 mg protein/g d.s) crude enzyme from Trichoderma harzianum LMLBP07 13-5 at 50°C and a substrate loading of 10 to 15% released 3.8 to 21.8 g/L and from T. longibrachiatum LMLSAUL 14-1 released 5.4 to 43.5 g/L glucose to the biomass. Ethanol was produced through separate hydrolysis and fermentation (SHF) of alkaline pretreated BPS hydrolysate using Saccharomyces cerevisiae UL01 at 30°C and 100 rpm. Highest ethanol produced was 17.6 g/L. Banana pseudostem was shown as a potentially cheap substrate for bioethanol production.

Semidry acid hydrolysis of cellulose sustained by autoclaving for production of reducing sugars for bacterial biohydrogen generation from various cellulose feedstock

Cellulosic biowastes are one of the cheapest and most abundant renewable organic materials on earth that can be, subsequent to hydrolysis, utilized as an organic carbon source for several fermentation biotechnologies. This study was devoted to explore a semidry acid hydrolysis of cellulose for decreasing the cost and ionic strength of the hydrolysate. For semidry acid hydrolysis, cellulose was just wetted with HCl (0 to 7 M) and subjected to autoclaving. The optimum molar concentration of HCl and period of autoclaving for semidry acid hydrolysis of cellulose were 6 M and 50 min respectively. Subsequent to the semidry acid hydrolysis with a minimum volume of 6 M HCl sustained by autoclaving, the hydrolysate was diluted with distilled water and neutralized with NaOH (0.5 M). The reducing sugars produced from the semidry acid hydrolysis of cellulose was further used for dark fermentation biohydrogen production by Escherichia coli as a representative of most hydrogen producing eubacteria which cannot utilize non-hydrolyzed cellulose. An isolated E. coli TFYM was used where this bacterium was morphologically and biochemically characterized and further identified by phylogenetic 16S rRNA encoding gene sequence analysis. The reducing sugars produced by semidry acid hydrolysis could be efficiently utilized by E. coli producing 0.4 mol H₂ mol^-1 hexose with a maximum rate of hydrogen gas production of 23.3 ml H₂ h^-1 L^-1 and an estimated hydrogen yield of 20.5 (L H₂ kg^-1 dry biomass). The cheap cellulosic biowastes of wheat bran, sawdust and sugarcane bagasse could be hydrolyzed by semidry acid hydrolysis where the estimated hydrogen yield per kg of its dry biomass were 36, 18 and 32 (L H₂ kg^-1 dry biomass) respectively indicating a good feasibility of hydrogen production from reducing sugars prepared by semidry acid hydrolysis of these cellulosic biowastes. Semidry acid hydrolysis could also be effectively used for hydrolyzing non-cellulosic polysaccharides of dry cyanobacterial biomass. The described semidry acid hydrolysis of cellulosic biowastes in this study might be applicable not only for bacterial biohydrogen production but also for various hydrolyzed cellulose-based fermentation biotechnologies.

Assessment of the effect of autohydrolysis treatment in banana's pseudostem pulp

Banana's pseudostem pulp (BPP) is a potential by-product obtained in the mechanical fiber extraction of banana's pseudostem. Its chemical characterization revealed to have an interesting composition, with a high polysaccharides content and low content in lignin, which makes it particularly relevant for the biorefinery's biochemical platform. Autohydrolysis pretreatment, studied under isothermal (140 °C) and non-isothermal conditions (140-220 °C), yielded oligosaccharides, mainly gluco-oligosaccharides, as the main soluble products. The highest oligosaccharides production (24 g/100 g raw material) was obtained at a severity factor of 2.3. Autohydrolysis pretreatment effectively disrupted the structure of the material, inducing an improvement of the enzymatic digestibility from 73% for the raw material up to 90% for the most severe conditions. Two stage autohydrolysis, with increasing severity, was also studied, allowing to obtain a higher amount of oligosaccharides (32 g/100 g raw material) and higher digestibility of the remaining solid (up to 97%).

Sequential chemical and enzymatic pretreatment of palm empty fruit bunches for Candida pelliculosa bioethanol production

Second-generation bioethanol production process was developed using pretreated empty fruit bunches (EFB). Consecutive acid/alkali EFB pretreatment was performed, first with HCl and then with NaOH with final washing steps for phenolic compounds elimination. Scanning electron microscopy images showed that EFB chemical treatments indeed attacked the cellulose fibers and removed the silica from surface pores. The optimization of enzymatic hydrolysis of EFB's cellulosic fraction was performed with 0.5%-4% v/v of Cellic® CTec2/Novozymes, different EFB concentrations (5%-15%, w/v), and hydrolysis time (6-72 H). Optimization essays were carried out in Erlenmeyer flasks and also in a 1 L stirred tank reactor. After enzymatic hydrolysis, a hydrolysate with 66 g/L of glucose was achieved with 2.2% (v/v) Cellic® CTec2, 15% (m/v) acid/alkaline pretreated EFB after 39 H of hydrolysis. A gain of 11.2% was then obtained in the 1 L stirred tank promoted by the agitation (72.2 g/L glucose). The hydrolysate was employed in bioethanol production by a new isolate Candida pelliculosa CCT 7734 in a separate hydrolysis and fermentation process reaching 16.6 and 23.0 g/L of bioethanol through batch and fed-batch operation, respectively. An integrated biorefinery process was developed for EFB processing chain.

Integrated Hydrolysis of Mixed Agro-Waste for a Second Generation Biorefinery Using Nepenthes mirabilis Pod Digestive Fluids

To sustainably operate a biorefinery with a low cost input in a commercial setting, the hydrolysis of lignocellulosic biomass must be undertaken in a manner which will impart environmental tolerance while reducing fermenter inhibitors from the delignification process. The challenge lies with the highly recalcitrant lignin structure, which limits the conversion of the holocelluloses to fermentable total reducing sugars (TRS). Due to these challenges, sustainable and innovative methods to pre-treat biomass must be developed for delignocellulolytic operations. Herein, Nepenthes mirabilis digestive fluids shown to have ligninolytic, cellulolytic and xylanolytic activities were used as an enzyme cocktail to hydrolyse mixed agro-waste constituted by Citrus sinensis (orange), Malus domestica (apple) peels, cobs from Zea mays (maize) and Quercus robur (oak) yard waste. The digestive fluids contained carboxylesterases (529.41 ± 30.50 U/L), β-glucosidases (251.94 ± 11.48 U/L) and xylanases (36.09 ± 18.04 U/L), constituting an enzymatic cocktail with significant potential for the reduction in total residual phenolic compounds (TRPCs), while being appropriate for holocellulose hydrolysis. Furthermore, the maximum TRS obtainable was 310 ± 5.19 mg/L within 168 h, while the TRPCs were reduced from 6.25 ± 0.18 to 4.26 ± 0.09 mg/L, which was lower than that observed when conventional methods were used. Overall, N. mirabilis digestive fluids demonstrated an ability to support biocatalytic processes with minimised cellulases hydrolysis interference. Therefore, the digestive enzymes in N. mirabilis pods can be used in an integrated system for feedstock hydrolysis in a second generation biorefinery.

Effect of iron salt type and dosing mode on Fenton-based pretreatment of rice straw for enzymatic hydrolysis

Fenton-based processes with four different iron salts in two different dosing modes were used to pretreat rice straw (RS) samples to increase their enzymatic digestibility. The composition analysis shows that the RS sample pretreated by the dosing mode of iron salt adding into H₂O₂ has a much lower hemicellulose content than that pretreated by the dosing mode of H₂O₂ adding into iron salt, and the RS sample pretreated by the chloride salt-based Fenton process has a much lower lignin content and a slightly lower hemicellulose content than that pretreated by the sulphate salt-based Fenton process. The higher concentration of reducing sugar observed on the RS sample with lower lignin and hemicellulose contents justifies that the Fenton-based process could enhance the enzymic hydrolysis of RS by removing hemicellulose and lignin and increasing its accessibility to cellulase. FeCl₃·6H₂O adding into H₂O₂ is the most efficient Fenton-based process for RS pretreatment.

Characterization of Enterococcus faecalis JF85 and Enterococcus faecium Y83 isolated from Tibetan yak (Bos grunniens) for ensiling Pennisetum sinese

Two bacteria strains with cellulolytic potential isolated from Tibetan yak (Bos grunniens) rumen were identified as Enterococcus faecalis (JF85) and Enterococcus faecium (Y83). Isolates grow well within a range of temperature 15 to 55 °C and pH 3.0-7.0, respectively. Two strains were inoculated with or without Lactobacillus plantarum (Lp) to Pennisetum sinese silage for 90 days. All inoculants increased lactic acid content, decreased pH and lignocellulose contents compared with silage without additives (control). The lowest pH, highest lactic acid and largest reduction in lignocellulose contents were observed in JF85+Lp and Y83+Lp silages. Isolates alone or in combination with Lp significantly increased WSC, mono- and disaccharides contents as compared to the control. Combined addition efficiently improved enzymatic hydrolysis of Pennisetum sinese silage, indicated by higher glucose yield and cellulose convertibility. Pennisetum sinese ensiled with combined additives is a suitable storage and pretreatment method prior to sugars production from energy crop.

Two-Step Thermochemical Cellulose Hydrolysis With Partial Neutralization for Glucose Production

Cellulose hydrolysis processes using concentrated acid usually involve two steps in order to obtain high glucose yields. The first step (pre-treatment) decrystallizes cellulose while the second step (post-hydrolysis) converts the amorphous cellulose to glucose. The two-step process developed by the Industrial Research Chair on Cellulosic Ethanol and Biocommodities and its industrial partner CRB Innovations Inc., includes an intermediate partial neutralization step, whose purpose is to decrease the amount of dilution water to be added for post-hydrolysis thus minimizing handling costs. In this work, the effect of several operating parameters on the glucose yield of this process was investigated using triticale cellulose and the best conditions yielding fermentable glucose (close to 100%) were determined. These conditions involve pre-treating cellulose at 30°C using 72 wt% H₂SO₄ with a H₂SO₄/dry cellulose mass ratio of 36 over 2 h, followed by a partial neutralization using 20 wt% NaOH at an H⁺/OH^- molar ratio of 2.3-2.5 and a post-hydrolysis at 121°C for 10 min. HIGHLIGHTS Influence of operating parameters on the glucose yield have been investigated.Conditions for producing cellulosic glucose with yields close to 100% have been identified.

Improved physicochemical pretreatment and enzymatic hydrolysis of rice straw for bioethanol production by yeast fermentation

Lignocellulosic biomass such as agricultural and forest residues are considered as an alternative, inexpensive, renewable, and abundant source for fuel ethanol production. In the present study, three different pretreatment methods for rice straw were carried out to investigate the maximum lignin removal for subsequent bioethanol fermentation. The chemical pretreatments of rice straw were optimized under different pretreatment severity conditions in the range of 1.79-2.26. Steam explosion of rice straw at 170 °C for 10 min, sequentially treated with 2% (w/v) KOH (SEKOH) in autoclave at 121 °C for 30 min, resulted in 85 ± 2% delignification with minimum sugar loss. Combined pretreatment of steam explosion and KOH at severity factor (SF 3.10) showed improved cellulose fraction of biomass. Furthermore, enzymatic hydrolysis at 30 FPU/g enzyme loading resulted in 664.0 ± 5.39 mg/g sugar yield with 82.60 ± 1.7% saccharification efficiency. Consequently, the hydrolysate of SEKOH with 58.70 ± 1.52 g/L sugars when fermented with Saccharomyces cerevisiae OBC14 showed 26.12 ± 1.24 g/L ethanol, 0.44 g/g ethanol yield with 87.03 ± 1.6% fermentation efficiency.

Ultrasound-assisted alkaline pretreatment for enhancing the enzymatic hydrolysis of rice straw by using the heat energy dissipated from ultrasonication

Rice straw samples were exposed to ultrasound-assisted alkaline (NaOH) pretreatment by using the heat energy dissipated from ultrasonication to increase their enzymatic digestibility for saccharification. The characterization shows that the pretreatment could selectively remove lignin and hemicellulose without degrading cellulose, and increase porosity and surface area of rice straw. The porosity, surface area and cellulose content of rice straw increased with the increasing concentration of NaOH used. The rice straw sample pretreated by using the heat energy dissipated from ultrasonication has a higher surface area and a lower crystallinity index value than that pretreated by using the external source of heating, and the amount of reducing sugar released from the former sample at 48h of enzymatic saccharification, which is about 3.5 times as large as that from the untreated rice straw sample (2.91vs. 0.85gL^-1), is slightly larger than that from the latter sample (2.91vs. 2.73gL^-1). The ultrasound-assisted alkaline pretreatment by using the heat energy dissipated from ultrasonication was proved to be a reliable and effective method for rice straw pretreatment.

Pretreatment of rice straw by ultrasound-assisted Fenton process

Fenton's reagent, ultrasound, and the combination of Fenton's reagent and ultrasound were used to pretreat rice straw (RS) to increase its enzymatic digestibility for saccharification. The characterization shows that compared with ultrasound, Fenton's reagent pretreatment was more efficient in increasing the specific surface area and decreasing the degree of polymerization (DP) of RS. The enzymatic hydrolysis results showed that the RS pretreated by ultrasound-assisted Fenton's reagent (U/F-RS), which exhibited the largest specific surface area and the lowest DP value, had the highest enzymatic activity, and the amount of reducing sugar released from U/F-RS at 48h of enzymatic saccharification is about 4 times as large as that from raw RS and 1.5 times as large as that from Fenton's reagent pretreated RS. The ultrasound-assisted Fenton process provides a reliable and effective method for RS pretreatment.

Depolymerization of microcrystalline cellulose by the combination of ultrasound and Fenton reagent

In this study, the combined use of Fenton reagent and ultrasound to the pretreatment of microcrystalline cellulose (MCC) for subsequent enzyme hydrolysis was investigated. The morphological analysis showed that the aspect ratio of MCC was greatly reduced after pretreatment. The X-ray diffraction (XRD) and degree of polymerization (DP) analyses showed that Fenton reagent was more efficient in decreasing the crystallinity of MCC while ultrasound was more efficient in decreasing the DP of MCC. The combination of Fenton reaction and ultrasound, which produced the lowest crystallinity (84.8 ± 0.2%) and DP (124.7 ± 0.6) of MCC and the highest yield of reducing sugar (22.9 ± 0.3 g/100 g), provides a promising pretreatment process for MCC depolymerization.

Selection of suitable mineral acid and its concentration for biphasic dilute acid hydrolysis of the sodium dithionite delignified Prosopis juliflora to hydrolyze maximum holocellulose

Two grams of delignified substrate at 10% (w/v) level was subjected to biphasic dilute acid hydrolysis using phosphoric acid, hydrochloric acid and sulfuric acid separately at 110 °C for 10 min in phase-I and 121 °C for 15 min in phase-II. Combinations of acid concentrations in two phases were varied for maximum holocellulose hydrolysis with release of fewer inhibitors, to select the suitable acid and its concentration. Among three acids, sulfuric acid in combination of 1 & 2% (v/v) hydrolyzed maximum holocellulose of 25.44±0.44% releasing 0.51±0.02 g/L of phenolics and 0.12±0.002 g/L of furans, respectively. Further, hydrolysis of delignified substrate using selected acid by varying reaction time and temperature hydrolyzed 55.58±1.78% of holocellulose releasing 2.11±0.07 g/L and 1.37±0.03 g/L of phenolics and furans, respectively at conditions of 110 °C for 45 min in phase-I & 121 °C for 60 min in phase-II.

Second generation bioethanol potential from selected Malaysia's biodiversity biomasses: A review

Rising global temperature, worsening air quality and drastic declining of fossil fuel reserve are the inevitable phenomena from the disorganized energy management. Bioethanol is believed to clear out the effects as being an energy-derivable product sourced from renewable organic sources. Second generation bioethanol interests many researches from its unique source of inedible biomass, and this paper presents the potential of several selected biomasses from Malaysia case. As one of countries with rich biodiversity, Malaysia holds enormous potential in second generation bioethanol production from its various agricultural and forestry biomasses, which are the source of lignocellulosic and starch compounds. This paper reviews potentials of biomasses and potential ethanol yield from oil palm, paddy (rice), pineapple, banana and durian, as the common agricultural waste in the country but uncommon to be served as bioethanol feedstock, by calculating the theoretical conversion of cellulose, hemicellulose and starch components of the biomasses into bioethanol. Moreover, the potential of the biomasses as feedstock are discussed based on several reported works.

Increased enzymatic hydrolysis of sugarcane bagasse from enzyme recycling

BACKGROUND

Development of efficient methods for production of renewable fuels from lignocellulosic biomass is necessary to maximize yields and reduce operating costs. One of the main challenges to industrial application of the lignocellulosic conversion process is the high costs of cellulolytic enzymes. Recycling of enzymes may present a potential solution to alleviate this problem. In the present study enzymes associated with the insoluble fraction were recycled after enzymatic hydrolysis of pretreated sugarcane bagasse, utilizing different processing conditions, enzyme loadings, and solid loadings.

RESULTS

It was found that the enzyme blend from Chrysoporthe cubensis and Penicillium pinophilum was efficient for enzymatic hydrolysis and that a significant portion of enzyme activity could be recovered upon recycling of the insoluble fraction. Enzyme productivity values (g glucose/mg enzyme protein) over all recycle periods were 2.4 and 3.7 for application of 15 and 30 FPU/g of glucan, representing an increase in excess of ten times that obtained in a batch process with the same enzyme blend and an even greater increase compared to commercial cellulase enzymes.

CONCLUSIONS

Contrary to what may be expected, increasing lignin concentrations throughout the recycle period did not negatively influence hydrolysis efficiency, but conversion efficiencies continuously improved. Recycling of the entire insoluble solids fraction was sufficient for recycling of adhered enzymes together with biomass, indicative of an effective method to increase enzyme productivity.

Enzymatic hydrolysis of steam exploded corncob residues after pretreatment in a twin-screw extruder

A modified twin-screw extruder incorporated with a filtration device was used as a liquid/solid separator for xylose removal from steam exploded corncobs. A face centered central composite design was used to study the combined effects of various enzymatic hydrolysis process variables (enzyme loading, surfactant addition, and hydrolysis time) with two differently extruded corncobs (7% xylose removal, 80% xylose removal) on glucose conversion. The results showed that the extrusion process led to an increase in cellulose crystallinity, while structural changes could also be observed via SEM. A quadratic polynomial model was developed for predicting the glucose conversion and the fitted model provided an adequate approximation of the true response as verified by the analysis of variance (ANOVA).

The improvement of enzymatic hydrolysis efficiency of rape straw and Miscanthus giganteus polysaccharides

The research was carried out with the aim to determine the impact of various combinations of cellulase and hemicellulase preparations on the effectiveness of enzymatic hydrolysis of polysaccharides of rape straw and Miscanthus giganteus after alkaline pretreatment. Their effectiveness was evaluated based on the quantity of saccharides released during enzymatic reaction and yield calculated in respect of the sum of polysaccharides present in native substrates. The complex of preparations produced from Trichoderma longibrachiatum fungi turned out to be the most effective. The study demonstrated a significant effect of xylanases from T. longibrachiatum, the presence of which evoked a 27-45% increase in the effectiveness of polysaccharides hydrolysis compared to the enzymatic complexes without their addition. In addition, results achieved in this study confirmed the necessity of applying the pretreatment in lignocellulose substrates conversion into bioethanol.

Saccharification of pumpkin residues by coculturing of Trichoderma reesei RUT-C30 and Phanerochaete chrysosporium Burdsall with delayed inoculation timing

Trichoderma reesei and Phanerochaete chrysosporium with different lignocellulose-degrading enzyme systems have received much attention due to their ability to biodegrade lignocellulosic biomass. However, the synergistic effect of the two fungi on lignocellulose degradation is unknown. Herein, a cocultivation of T. reesei RUT-C30 and P. chrysosporium Burdsall for biodegradation of lignocellulosic pumpkin residues (PRS) was developed to produce soluble saccharide. Results indicated that a cocultivation of the two fungi with P. chrysosporium Burdsall inoculation delayed for 1.5 days produced the highest saccharide yield of 53.08% (w/w), and only 20.83% (w/w) of PRS were left after one batch of fermentation. In addition, this strategy increased the activities of secreted cellulases (endoglucanase, cellobiohydrolase, and β-glucosidase) and ligninases (lignin peroxidase and manganese peroxidase), which correlated to the increased saccharide yield. Besides, the resulting monosaccharides including glucose (1.23 mg/mL), xylose (0.13 mg/mL), arabinose (0.46 mg/mL), and fructose (0.21 mg/mL) from cocultures exhibited much higher yields than those from monoculture, which provides basal information for further fermentation research. This bioconversion of PRS into soluble sugars by cocultured fungal species provides a low cost method based on lignocellulose for potential biofuels or other bioproduct production.

Evaluation of pretreatment methods for enzymatic saccharification of wheat straw for bioethanol production

Pretreatment is an essential step in the enzymatic hydrolysis of biomass and subsequent production of bioethanol. The current study is focused on two different pretreatment methods of wheat straw using mild temperatures (100°C for 2h and RT for overnight). In one method, native substrate was treated with 1.5% (w/v) NaOH at two different above mentioned conditions followed by acid hydrolysis (0.75% (v/v) sulfuric acid at 100°C for 2h). In another method, the native substrate was initially treated with acid (0.75% (v/v) sulfuric acid at 100°C for 2h) followed by treatment with 1.5% (w/v) NaOH at two different above conditions. After the pretreatments, the residues were treated with Accellerase 1500 (26U/g) and maximum yield of glucose (65.2gL(-1)) were found with 0.75% sulfuric acid (100°C for 2h) followed by alkali (1.5% NaOH at 100°C for 2h). Fermentation of this hydrolyzate using Saccharomyces cerevisiae strain produced 24.4gL(-1) of ethanol with corresponding yield of 0.44g/g.

Enzymatic hydrolysis optimization of microwave alkali pretreated wheat straw and ethanol production by yeast

Microwave alkali pretreated wheat straw was used for in-house enzyme production by Aspergillusflavus and Trichodermareesei. Produced enzymes were concentrated, pooled and assessed for the hydrolysis of pretreated wheat straw. Factors affecting hydrolysis were screened out by Placket-Burman design (PBD) and most significant factors were further optimized by Box-Behnken design (BBD). Under optimum conditions, 82% efficiency in hydrolysis yield was observed. After the optimization by response surface methodology (RSM), a model was proposed to predict the optimum value confirmed by the experimental results. The concentrated enzymatic hydrolyzate was fermented for ethanol production by Saccharomyces cerevisiae, Pichia stipitis and co-culture of both. The yield of ethanol was found to be 0.48 g(p)/g(s), 0.43 g(p)/g(s) and 0.40 g(p)/g(s) by S. cerevisiae, P. stipitis and by co-culture, respectively, using concentrated enzymatic hydrolyzate. During anaerobic fermentation 42.31 μmol/mL, 36.69 μmol/mL, 43.35 μmol/mL CO(2) was released by S. cerevisiae, P. stipitis and by co-culture, respectively.